For the manner in which men live is so different from the way in which they ought to live, that he who leaves the common course for that which he ought to follow will find that it leads him to ruin rather than safety.
-Machiavelli

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Wednesday, January 25, 2012

Hollow grinding

One of the few power tools I have is my suicide grinder. Portions of the rebuild have been posted here. It's a belt driven General. It's old as dirt, but the new belt and bearings did it some good. Since last posting about it, I've gotten it bolted down to the table in my basement. I also picked up a Veritas grinding rest. Let's have a look...
One of the blades for my block plane. That bevel is flat. To resharpen it on stones would mean honing away all that metal on the cutting edge down to a 20 degree angle to reestablish the primary bevel. Then we'd have to adjust and hone the secondary bevel (in this case 25 degrees). Yuck! That's a lot of work, and that's why I have a grinder now.


Here, I have the tool rest set to 20 degrees. This rest is easy to set up, and easy to adjust. I'm glad I got it.

I have a stack of old Norton stones. This one ran with the least vibration. It's only 1/2" wide, but it works very well for me. I cut it to a crowned shape. I like the results I'm getting better than when I had a wide, flat wheel. Try it out if you get the chance.
Here's the new primary bevel. There is a light strip at the very leading edge as I didn't grind all the way up. That will become the secondary bevel when I move to the honing stones.
The ultimate purpose of a hollow grind is to remove metal in order to make the entire sharpening process more efficient. You don't have to wear out your stones by recutting the primary bevel. When the secondary bevel grows to be too large, you take the iron to the grinder and in no time at all, you can reestablish the hollow behind the cutting edge.

3 comments:

  1. Very nice, I can’t wait to see more pics of the suicide grinder (I love old machinery) and the infill's. I personally sand the first and secondary bevel, but I have grinded them before with the same luck.
    Kelton Goold
    gooldworkshop.blogspot.com

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  2. Good to read that you brought a piece of machinery back to life. I personally don't like secondary bevels and I don't use them at. But I can see with your set up it how easy it is to do and to maintain.
    ralph

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  3. Kelton: I used to sand my primary bevels as well, just to save the wear on my stones.
    Ralph: Is there a reason you don't like doing a secondary bevel? Hollow grinding became sort of necessary for me when I started making my own planes. My shop made irons are a full 1/4" thick, without grinding them, I'd be on the stones all day!

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